Permeability testing method and apparatus

Claim 1

AN APPARATUS FOR TESTING THE FLUID PERMEABILITY OF AN ELEMENT COMPRISING MEANS FOR PASSING A FLOW OF FLUID UNDER A SUBSTANTIALLY CONSTANT PRESSURE FROM ONE SIDE OF A REFERENCE ELEMENT TO THE OTHER SIDE THEREOF, MEANS FOR DETERMINING THE PRESSURE ON THE OTHER SIDE OF SAID REFERENCE ELEMENT AS A RESULT OF SAID FLOW, SAID FIRST-NAMED MEANS BEING OPERABLE TO PASS A FLOW OF FLUID UNDER SAID CONSTANT PRESSURE FROM ONE SIDE OF A TEST ELEMENT TO THE OTHER SIDE THEREOF, SAID SECOND-NAMED MEANS BEING OPERABLE TO DETERMINE THE PRESSURE ON THE OTHER SIDE OF SAID TEST ELEMENT AS A RESULT OF SAID LAST-NAMED FLOW, MEANS FOR COMPARING SAID PRESSURES RESULTING FROM SAID FIRST AND SECOND-NAMED FLOWS, AND MEANS FOR SUPPLYING A METERED FLOW OF FLUID FROM SAID ONE SIDE TO SAID OTHER SIDE OF SAID TEST ELEMENT WITHOUT PASSING THERETHROUGH UNTIL SAID PRESSURE COMPARING MEANS INDICATES THAT THE PRESSURE ON SAID OTHER SIDE OF SAID TEST ELEMENT SUBSTANTIALLY EQUALS THE PRESSURE ON SAID OTHER SIDE OF SAID REFERENCE ELEMENT, WHEREBY THE AMOUNT OF SAID METERED FLOW OF FLUID INDICATES THE FLUID PERMEABILITY OF SAID TEST ELEMENT RELATIVE TO SAID REFERENCE ELEMENT.